Apparatus for congelation of ground



y 4, 1953 J. P. DAXELHOFER Y APPARATUS FOR CONGELATION OF GROUND Filed June 21, 1948 INVENTOR plied with a liquefied gas which is Patented July 14, 1953 OFFICE APPARATUS FOR OONGELATIQN OF OUND J eanPierre Daxelhofer, Zurich, Switzerland Application June 21, 1948, Serial N 0. 34,236 In Switzerland June 23, 1947 (or. sz-si 2 Claims.

This invention relates to a method of congelation of ground and to apparatus for carrying out this method.

The direct expansion of a liquefied gas in refrigerating tubes for the purpose of artificial congelation of ground offers many advantages, and attempts to use this method have been made for a number of years. Various processes have been tried out, but the only system having practically been applied uses liquefied carbon dioxide which is continuously supplied to each refrigerator, the supply being controlled by means of a calibrated orifice.

The advantages of direct expansion as compared With the use of brine are obvious. However, the known methods have several serious practical defects, of which the principal ones are the difiiculty of making sufiiciently tight high pressure conduits, the complicated control of special nozzles the dimensions of which should vary according to the wall thickness of the conduits and refrigerators and to the decrease of the efficiency of the refrigerating central, the frequent obstruction of these nozzles, the necessity of providing numerous valves and accessory removable pieces which constitute a permanent danger of leakage.

The object of the present invention is to overcome the mentioned difficulties by the provision of a method of congelation of ground according to which the refrigerator tubes are discontinuously or intermittently supplied by a liquefied gas which is expanded before entering into the refrigerating tubes.

A further object of the invention is the provision of apparatus for carrying out the above method, and which comprises an expansion chamber for the liquefied gas, which is placed between the high pressure supply container of liquefied gas and the refrigerator tubes. A measuring chamber may be provided in the circuit of the refrigerating agent for the precise determination of the quantity of fluid distributed to each refrigerating tube of the apparatus.

The method according to the invention accordingly substitutes a discontinuous supply of refrigerating agent to the heretofore used continuous supply, and instead of supplying the refrigerators with a liquefied gas at high pressure, the refrigeratorsaccording to the invention are suppreviously expanded in an intermediary container;

The essential details of the method and the apparatus according to my invention will be more fully disclosed in the followingspecification; ref- 'erence being had to the a companying drawing,

in which,

Fig. 1 is a diagrammatic layoutof the apparatus in sectional elevation, while Fig. 2 illustrates a modification of a detail of a refrigerator tube.

The represented apparatus comprises a gas compressor l which can be a single stage or a multiple stage compressor. The output of the compressor, for example compressed carbon dioxide gas passes into an oil separator 2 and from there to a condenser 3. The liquefied gas flows into a high pressure chamber 4 having an oil outlet [9. This chamber 4 preferably has a sufficient capacity to be able to accumulate the quantity of fluid which circulates in the system. The liquid gas flows from the chamber 4 to the expansion chamber 6; a valve 5 controls the flow of liquid into the chamber 5. The expansion chamber 6 is provided with a pressure gauge 1 indicating the pressure Within the chamber which latter is also connected to the suction conduit I4 of the compressor I by means of a conduit 2U controlled by a valve 8 which allows control of the'pressure in the chamber 6 and accordingly of the temperature of the liquid accumulated in the expansion chamber 6.

At the beginning of the congelation of the ground a temperature of the refrigerating agent of, for example, 20 centigrade is chosen, which corresponds to a pressure of about 20 atmospheres absolute. When freezing of the ground is in progress the temperature of the refrigerating agent can be lowered, for example to -50 centigrade which corresponds to a pressure of about '7 atmospheres absolute.

From the expansion chamber 6 the liquid gas passes into a measuring chamber 9 provided with a level or capacity indicator 2|; the volume of this chamber 9 preferably is equal to the Volume of one or of more refrigerating tubes I I.

A conduit 22 connects the measuring chamber 9 to refrigerating tube or tubes H which are lowered in the ground to be frozen, the conduit 22 being provided with an outflow valve l0 for the chamber 9. When the valve I0 and the inlet valve I 2 of the refrigerating tube II are both open, the liquid charge in the measuring chamber is directly emptied in the refrigerating tube. This latter is connected by the intermediary of a valve [3 to the suction conduit 14 of the compressor.

During congelation of the ground the valve 13 remains open so that the refrigerator tube ll constantly communicates with the suction conduit Hi. When a tube l l is filled with the liquid gas arriving from the measuring chamber 9, the

valve 12 in the supply conduit 22 is closed. The charge in the tube l I then gradually evaporates until the tube will be completely empty. During this period the filling of other tubes of the congelation system proceeds, until all tubes of the system have been filled once, and then the filling of the first tube is started again. This procedure is continued until the desired section of ground is frozen to enable the contemplated structural work to be carried out and maintained.

The progress of emptying of a refrigerator tube or a group of tubes H is controlled by means of the valve 13 and of a pressure gauge 23. When the inlet valve 12 is closed and the suction control valve l3 is also closed, the pressure indication of the gauge 23 remains constant as soon as the tube is empty, but when there is still some liquid left in the tube H, the pressure increases when both valves are closed, and the gauge 23 indicates this increase. In this manner it can be easily determined when the refilling of a tube must be started.

The apparatus may, comprise a special reservoir in order to ensure the filling of the system and compensate losses due to leakage, by means of solid carbon dioxide. When this reservoir I5 is shut off from the system by a valve l8 and is placed in communication with the atmosphere through valve H, the gate Hi can be opened and a provision of solid carbon dioxide filled into the reservoir. When the valve l1 and the gate is are both closed the pressure increases in the reservoir [5; when it has passed the triple point, the charge of dry ice has become liquefied and when now the valve IE5 is opened additional liquid gas is introduced into the system.

The control means for draining the refrigerator tube ll represented in Fig. l are given by way of example only. Fig. 2 shows modified control means for emptying the tube. In this example a small tube 24 extends into the refrigerator tube 1 la almost to the bottom thereof. Outside of the tube I la, the tube 24 is provided with a valve 25. 22 is the supply conduit feeding liquefied gas in the tube Ila, and the conduit 26 is connected to the suction conduit of the compressor. As long as liquefied gas is present in the tube 1 la, and the valve 25 is gradually opened, the expelled liquid is transformed to snow at the outlet of the tube 24; but when the liquid in the tube Ha has completely evaporated, only gas escapes through the tube 24 Without leaving a snow deposit at the outlet. This indicates that the tube 1 la needs refilling.

Another method of ascertaining whether the refrigerator tube is empty is to dispose an electric temperature indicator on the bottom of the tube. When the tube is filled with liquid gas, the temperature at the bottom is higher than the temperature in the suction conduit of the compressor. When th refrigerator tube H has for example a length of meters and when the suction is supposed to be 8.5 atmospheres absolute, which corresponds to a temperature of -45 centigrade, the temperature at the bottom of the tube will be substantially ll.5 C. When the level of the liquid lowers and reaches the temperature indicator, the temperature first decreases to 45 centigrade, and when all the liquid is evaporated, the temperature rises again; an electrical contact indicator device for showing when a freezing tube is emptied, may also be employed, as may any other suitable device.

The described congelation method offers the following advantages: The production of cold in each refrigerator tube l l is exactly known, as well as the total production of cold of the system, which is not possible in the known methods, since it may happen in known systems that a refrigerator tube is partially filled with gas instead of being filled entirely with liquid, owing to irregular supply or local expansion at valves, pipe bends, or due to leakages. In the described system, all refrigerator tubes are uniformly filled with refrigerating liquid by means of the measuring chamber.

The temperature in each refrigerator tube corresponds to the deepest temperature which is desired. When for example the entrance of the supply conduit 22 into the tube ll is formed by a peripheral slot extending over a major portion of the circumference of the tube, the liquid will drizzle down along the interior wall of the tube during the filling operation, and in the beginning the upper portion of the tube will be cooled off more intensely. As soon as the entire tube is cold and the liquid starts to accumulate at the bottom thereof, the coldest point is at the bottom; when the liquid level rises during progress of the filling, the point of minimum temperature also rises. Afterwards, when the supply is shut off, the liquid level and accordingly the point of minimum temperature lowers again to the bottom. During each filling of a refrigerator tube, each horizontal section of the tube is three times subjected to the minimum temperature, which is not the case with the freezing tubes of known apparatuses with continuous feed.

The described method of direct expansion of a liquefied gas can be applied to refrigerator tubes of any length. Supposing in fact on the contrary a tube with a continuous feed having a depth of 50 m. in condition of equilibrium, that is to say full of liquid which evaporates, there will be formed a thick layer of ice around the tube which prevents or limits the supply of heat to the liquefied gas in the interior of the tube. The suction pressure being supposed as 8.5 atmospheres corresponding to -45 c'entigrade, the pressure at the bottom of the tube will be 14.1 atmospheres, which corresponds to a temperature of about 32 centigrade. There accordingly exists a temperature difference of 13 between the top and the bottom of the refrigerator tube. This difference will be much more pronounced when instead of using carbon dioxide as refrigerating agent another gas such as for example ammoniac (NHa) is used.

Owing to first expanding the liquefied gas, the supply conduits to the refrigerator tubes are under low pressure, as also the various valves and other control apparatus, and these conduits can be effectively insulated so as to reduce losses in the circuit.

I claim:

1. Apparatus for the congelation of ground, comprising a compressor for a gaseous carbon dioxide, as refrigerating agent, a condenser for liquefying the compressed gas, an expansion chamber for reducing the pressure of the liquefied gas, a measuring chamber connected to the expansion chamber, refrigerator tubes connected to the measuring chamber, control means for supplying measured quantities of liquefied refrigerating agent to the refrigerator tubes, a suction conduit establishing communication between the refrigerator tubes and the compressor, and a reservoir adapted to contain a supply of solid carbon dioxide and communicating with the refrigerating circuit to compensate losses of the refrigerating agent in the system.

2. Apparatus for the congelation of ground, comprising a compressor for a gaseous refrigera ing agent, a condenser for liquefying the compressed gas, an expansion chamber connected to the condenser, a measuring chamber connected to the expansion chamber, refrigerator tubes connected to the measuring chamber, control means for supplying a measured quantity of liquefied refrigerating agent to the refrigerator tubes, a suction conduit establishing communication between the refrigerator tubes and the compressor, and means for controlling egress of refrigerant from said refrigerator tubes.

JEAN PIERRE DAXELHOFER.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Schmidt Aug. 30, 1904 Voorhees Sept. 7, 1909 Miles Nov. 11, 1919 Pomykala Mar. 5, 1929 Dittmer July 4, 1944 FOREIGN PATENTS Country Date Great Britain Aug. 18, 1904 Great Britain 1930 France 1920 Great Britain Dec. 27, 1939 

